1. Field of the Invention
The present invention relates to communication systems, transmission devices and methods thereof, and reception devices and methods thereof. More particularly, the present invention relates to a communication system, a transmission device and a method thereof, and a reception device and a method thereof, which are capable of transmitting/receiving beacon signals while the power consumption is suppressed in accordance with the update frequency of information.
2. Description of the Related Art
In a wireless network, a communication terminal used for transmission buffers data to be transmitted to a communication terminal which is in a hibernation mode for the purpose of preventing packet loss. A beacon signal transmitted in a specific cycle triggers activation of the communication terminal which is in a hibernation mode. Specifically, when the communication terminal in a hibernation mode finds a mark attached to the beacon signal which indicates that the beacon signal is to be transmitted to the communication terminal, the communication terminal is activated and receives the data.
In general, a beacon signal includes important information necessary for maintaining line connection. Accordingly, complicated high-level processing is necessary for reception processing and transmission processing of the beacon signal. In the related art, software processing by means of a CPU (Central Processing Unit) is employed for the reception processing and the transmission processing of the beacon signal.
As shown in FIG. 1, since a beacon signal is transmitted in a substantially constant cycle for each superframe, a CPU performs processing in the substantially constant cycle. Accordingly, even when the CPU is in a hibernation mode for suppressing the power consumption, the CPU is activated for the reception processing or transmission processing of the beacon signal. Consequently, it is hard to meet the demand for suppressing the power consumption to an extremely low level while the CPU is waiting for communication.
Japanese Unexamined Patent Application Publication No. 2005-33586 discloses a technique of reducing the power consumption of a wireless communication device.